I. Field of the Invention
The invention generally relates to cellular telephones and in particular to cellular telephones configured for receiving and transmitting data.
II. Description of the Related Art
Computer users often utilize wireless cellular telephone systems to engage in mobile data communications. Presently, there are two prominent types of cellular telephone systems: analog cellular telephone systems, commonly referred to as AMPS systems, and digital cellular telephone systems, which include code division multiple access (CDMA) systems and time division multiple access systems (TDMA). To perform data communications via a circuit switched connection using an AMPS cellular telephone system, the digital data must first be converted into tones via the use of a modem. Modems are also employed for communication via the standard wirebased public switch telephone network (PSTN). To network using a digital cellular telephone system, the digital data is provided directly to the cellular telephone which processes the data in its digital form. To allow for maximum flexibility, most digital cellular telephones can properly interface with both digital cellular telephone systems as well as AMPS cellular telephone systems.
To interface a portable "laptop" computer with a cellular telephone configured for analog operation, the user generally uses a modem configured in the shape of a thin card that is placed in a slot in the computer. The modem outputs tones which can then be fed into the cellular telephone via the use of a cable. This configuration of both the modem and the computer is in accordance with the Personal Computer Memory Card International Association (PCMCIA) standard, which was adopted in order to facilitate ease of use and mobility. To interface the laptop computer with a cellular telephone configured for digital operation, a digital output port of the computer must be coupled to the cellular telephone, also via the use of a cable. The digital output port is typically configured in accordance with the RS-232 standard which calls for the digital data to be output in digital signals of plus or minus twelve volts.
FIG. 1 illustrates a laptop computer and cellular telephone configured for mobile networking. A laptop computer 2 and a cellular telephone 4 are shown along with an RS-232 cable 5 for CDMA and an AMPS connection line 7. The laptop computer includes a serial port 6 for the RS-232 line and a slot for receiving a PCMCIA card 8 connected to the AMPS connection cable. The cellular telephone includes only a single input terminal 9. Hence, either the RS-232 cable or the AMPS cable, but not both, can be connected to the cellular telephone. Thus, the user must know in advance which connection line is required and connect the correct connection line to the cellular telephone.
For the foreseeable future, both AMPS and digital telephone systems are expected to coexist, and therefore a cellular telephone user will need to have the capability to interface with both types of systems. As described above, however, two different methods for interfacing the laptop computer with the cellular telephone and the associated signal processing are required for the two different systems. The use of two different methods for interfacing is inconvenient for the user, as he or she must reconfigure the connection between the computer and phone depending on the type of interface being conducted. Thus, a method for allowing wireless networking to be conducted in accordance with both digital and analog operation without the need for reconfiguration would be highly desirable. One such method is described in copending U.S. Pat. application Ser. No. 08/636,261 entitled "DATA COMMUNICATION USING A DUAL MODE RADIOTELEPHONE" assigned to the assignee of the present invention and incorporated herein by reference.
Another problem in providing mobile networking using both the AMPS and CDMA interface relates to selecting which of various data transmission protocols, formats and compression standards are to be provided. Recently, a wide range of protocols, formats and compression standards have been developed for facilitating data transmission each requiring its own unique software, hardware, or both. The methods include error correction protocols as well as packet interface protocols such as TCP/IP. The cost and power consumption associated with supporting these various methods is typically substantial relative to the normal computing capacity of a cellular telephone. While additional computing capacity could be incorporated into the phone, this would increase the phones cost, size and power consumption, which adversely affects mobility. Additionally, these desired protocols may change over time, causing the software in the phone to become obsolete. Accordingly, it is not necessarily feasible, or even desirable, to provide for all possible data transmission protocols within a cellular telephone. Therefore, it is desirable to configure and arrange the necessary hardware and software in a manner which allows networking to take place, but which also minimizes costs and power consumption to the cellular telephone itself, and which facilities upgrades to the type of networking that can be conducted. It is to these ends that the invention is also drawn.